Accusative with Participle vs. Subject-related Participle

We saw them crossing the street. = They were crossing the street. I saw them.

So-called 'Accusative with the Participle'. The participle relates to 'them'.

There are several ways to make this participle relate to the subject of the main clause (as an adverbial modifier of manner - sorry for the maybe-obsolete terminology):

We saw them when/while crossing the street.

(When/While) Crossing the street, we saw them.

1) Are there any other ways to rephrase the sentence (preserving the general outline of it, of course) so that it was the latter case?

2) Can this participle crossing in We saw them crossing the street be disconnected from 'them' and related to 'We' by just a change of intonation in speech (perhaps a pause + a lower tone + higher rate) or by just using a comma in writing?

3) If yes, is there still an element of comicality to a sentence like this one left:

I noticed a few new billboards, walking along the street?

4) If yes, is there an element of ambiguity (even with a comma in place) preserved in:

I noticed a few vendors (machines or people?), walking along the street (who was walking?)?

Thank you very much in advance. Tried to cram all possible aspects of my issue into one post.

YETY